Nowadays, rechargeable batteries, e.g. comprising NiCd cells, are commonplace for powering a large variety of portable electronic apparatus.
By way of example, rechargeable batteries can be used in hand-held cellular radio telephones, so that the subscriber equipment is truly portable. However, particularly because of their transmission capability, portable cellular telephones consume a significant amount of power, necessitating relatively frequent recharging of the batteries.
It is believed that the useful life of a rechargeable battery depends on how it is treated and in particular on the manner in which it is charged under different conditions. In other words, it is possible to optimize the useful operating life of a rechargeable battery by adopting an appropriate charging regime.
U.S. Pat. No. 4,684,870 discloses apparatus for charging a rechargeable battery in a handheld transceiver while maintaining communications capability. The battery charger comprises a dual-mode charging circuit which automatically generates different voltages during receive and transmit modes respectively.
British Patent Application GB-A-2,219,151 discloses a charger for rechargeable batteries which automatically selects between fast, semi-fast and trickle charging depending on the type of battery being charged.
European Patent Application EP-A-0,340,794 discloses apparatus for charging an interchangeable battery pack in a portable radio telephone. The battery pack comprises a switch, the position of which indicates the capacity of the battery pack. The separate charger comprises respective charging circuits for providing two different charging currents, which are selectively connected to the battery in accordance with the identification given by the switch, thus providing optimum charging current for the particular battery type being used.